Analysis of the PI3K-AKT-mTOR pathway in penile cancer: evaluation of a therapeutically targetable pathway
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Anthony Adimonye1, Elzbieta Stankiewicz1, Sakunthala Kudahetti1, Giorgia Trevisan2, Brendan Tinwell3, Cathy Corbishley3, Yong-Jie Lu1, Nick Watkin4 and Daniel Berney1
1Centre for Molecular Oncology, Bart’s Cancer Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
2Department of Histopathology, Royal London Hospital, Barts Health NHS Trust, London, United Kingdom
3Department of Cellular Pathology, St George’s Hospital, London, United Kingdom
4Department of Urology, St George’s Hospital, London, United Kingdom
Anthony Adimonye, email: [email protected]
Keywords: phosphatidylinositol-4,5-bisphosphate 3- kinase; catalytic subunit alpha; penile squamous cell carcinoma; copy number gain; p-AKT
Received: December 30, 2017 Accepted: February 27, 2018 Published: March 23, 2018
Objectives: To determine whether phosphatidylinositol-4,5-bisphosphate 3- kinase, catalytic subunit alpha (PIK3CA) copy number gain is common and could prove a useful marker for the activation status of the PI3K-AKT-mTOR pathway in penile squamous cell carcinoma (PSCC).
Methods: Fresh frozen tissue and archival blocks were collected from 24 PSCC patients with 15 matched normal penile epithelium (NPE) tissue from St George’s Hospital. PIK3CA mutational and copy number status (CNS) was assessed via Sanger sequencing and fluorescence in-situ hybridisation, respectively. PIK3CA RNA expression was quantified using TaqMan gene expression assay. HPV DNA was detected with INNO-LiPA assay. p-AKT and p-mTOR protein expression were assessed using western blot and immunohistochemistry.
Results: PIK3CA copy number gain was found in 11/23 (48%) patients, with mutations present in only 2/24 (8%) patients. In comparison to NPE, PSCC showed significantly lower PIK3CA RNA expression (p=0.0007), p-AKT (Ser473) nuclear immunoexpression (p=0.026) and protein expression of p-AKT (Thr308) (p=0.0247) and p-mTOR (Ser2448) (p=0.0041). No association was found between PIK3CA CNS and p-AKT and p-mTOR protein expression.
Conclusion: Based on our results the PI3K-AKT-mTOR pathway is not a key driver in PSCC carcinogenesis and the therapeutic targeting of this pathway is unlikely to produce significant clinical benefit.
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